Rasterization

Rasterization is the foundational rendering technique that converts 3D geometry into 2D pixels on screen. It has been the dominant method for real-time graphics since the earliest 3D hardware accelerators in the 1990s and remains the workhorse behind virtually every game, interactive application, and real-time 3D experience today — even as ray tracing emerges as a complementary approach.

The rasterization pipeline follows a well-defined sequence. Vertex processing transforms 3D vertices through model, view, and projection matrices into screen space. Primitive assembly groups vertices into triangles. Rasterization proper determines which pixels each triangle covers, generating fragments. Fragment processing — executed by pixel shaders — computes the final color of each pixel based on textures, lighting, and material properties. Depth testing ensures closer objects occlude farther ones. The result is written to a framebuffer for display.

Rasterization's great strength is speed. Because it processes geometry one triangle at a time in a streaming fashion, it maps perfectly to massively parallel GPU architectures. Modern GPUs can rasterize billions of triangles per second. This throughput advantage over ray tracing (which must trace individual rays through the scene) is why rasterization remains the primary rendering method for real-time applications, even though ray tracing produces more physically accurate results for reflections, shadows, and global illumination.

The modern rendering landscape is a hybrid. Games use rasterization for primary visibility (determining what's on screen) while selectively using ray tracing for specific effects — reflections, shadows, ambient occlusion, and global illumination. Unreal Engine 5's Lumen, for instance, blends software ray marching, hardware ray tracing, and rasterized screen-space techniques. Path tracing — full ray tracing for all lighting — remains the aspiration for real-time graphics, but rasterization will likely remain the backbone of interactive rendering for years to come, augmented rather than replaced by ray-based techniques.